Fluid overload can be caused by many things including metabolic disease, renal failure and, especially, congestive heart failure (CHF), which has become a disease of epidemic proportions all over the globe. CHF is a progressive deterioration of the heart muscle that leads to an inability to pump enough blood to support the vital organs. Deterioration of the heart muscle leads to decreased pumping capacity and increased fluid retention caused by the lack of perfusion pressure of the kidneys due to the failure of the heart to pump enough blood at the proper pressure. Fluid overload can cause leg swelling, shortness of breath and water accumulation in the lungs, impairing the ability to properly breathe.
The incidence of class III and IV congestive heart failure (CHF) continues to grow along with the growing incidence of diabetes, obesity, coronary heart disease, Diastolic Dysfunction and other related ailments. In addition, the medically improved outcomes from Ischemic Heart Disease and Myocardial Infarction are generating an increased population of people suffering from varying degrees of CHF.
Treating patients with CHF is presently one of the major expenses in the healthcare bill of any westernized nation. Furthermore, treating patients with CHF is one of the most significant causes of financial loss in the U.S. hospital industry.
Removal of excess fluids from the body can be accomplished with diuretics and other drugs that improve the performance of the heart muscle.
Thanks to numerous pharmacological agents such as ACE inhibitors, diuretics and beta blockers, the morbidity and mortality of CHF has become somewhat improved. Pacemakers and implantable defibrillators have aided in this regarding also.
Regardless of the advancements in medical technology some of the major patient problems associated with CHF are fluid overload and sodium retention. Both fluid overload and sodium retention are associated with various endocrine derangements and release noxious cytokines that may further aggravate the CHF condition. These drugs become gradually ineffective over time and may also cause undesirable effects such as kidney failure.
There is a growing body of literature supporting the conclusion that the physical removal of fluid by convection (i.e., ultrafiltration) of blood can significantly improve patient outcomes and shorten hospital stays and intensive care unit utilization. Fluid removal may be superior to the administration of very large losses of diuretic drugs.
Advantages of ultrafiltration over diuretic drugs include: (1) efficient fluid removal without side effects such as kidney failure and blood pressure drops; (2) prompt relief from shortness of breath and swelling; and (3) improvement regarding certain adverse hormonal effects that are associated with CHF.
Ultrafiltration is performed by pumping blood from a catheter in an artery or a large vein, though a blood filter or a dialyzer while creating a gradient of pressure through the filter membrane. The pressure gradient forces the passage of fluid out of the blood by convection and the fluid is drained out.
Conventional ultrafiltration devices suffer from several drawbacks. Usually, these devices are cumbersome, heavy and must be hooked to electrical outlets for power. Since ultrafiltration patients must remain connected to these devices for many hours, their ability to perform normal every day activities is severely limited. In addition, typical ultrafiltration treatments are geared for fast removal of several liters of excess fluid. However, the fluid removal is only temporary and the excess fluid usually reaccumulates in the patient's body after a short period of time. The reaccumulation of fluid is harmful to the patients, as the kidneys are further injured by the progress of CHF and the side effects of the diuretic drugs used to treat the heart.
Presently ultrafiltration devices are not designed to economically provide a single patient prolonged or continuous ultrafiltration. In addition, acute treatments performed over 4 to 6 hours of hemofiltration on a patient, can be efficient and capable of removing up to around 23 liters of excess fluid from a patient in one session, but are not physiologically good for the patient and can be conducive of blunt shifts in fluid content in various compartments of a patient's body. Such large amounts of fluid removal may also create hypotension and hemodynamic instability. Furthermore, the present ultrafiltration methods do not provide for a steady removal of excess fluids and sodium from the patient's body.
A further problem with ultrafiltration devices is that repeated reconnection to an ultrafiltration device requires accessing blood flow by puncturing a large blood vessel and forming an arteriovenous shunt. These shunts only last for limited periods of time and are subject to infection, clotting and other complications that result in numerous hospitalizations and repeated surgical interventions. Similar problems also exist when a patient's blood stream is accessed by alternative methods, such as by inserting large catheters into large veins and arteries.
In view of the above disadvantages, there is a substantial need for a portable ultrafiltration device that provides continual, steady and smooth removal of excess fluid from the body.